The argon-oxygen-decarburization (AOD) process is a common metallurgical treatment to decarburize high-chromium steel melts using oxygen and inert gas injection through sidewall tuyeres and a toplance. AOD converters are characterized by a fast and efficient decarburization, whereby the oxidation of chromium is reduced compared to treatments for regular steel grades like the LD process. However, lowfrequency oscillations with large amplitudes can occur during the process and influence the converter's structural integrity. The aim of plant engineering is the development of an AOD converter using a vessel design that provides a fast decarburization rate and effective mixing, whereby the oscillation's amplitude and the chromium losses are as low as possible. The oscillation of the vessel is induced by the fluid flow. In this study a numerical model is presented, where the oscillation model is integrated in the CFD (computational fluid dynamics) solver by subroutines. The numerical models for both, fluid flow and vessel oscillation, are validated by experiments carried out with a 1:4 scale water model. In a further step, the numerical models are transferred to the actual AOD process. The results of the simulations are compared to experimental results obtained in plant trials. The numerical model developed in the present study can be used as a tool to design AOD vessels that fulfill the above mentioned criteria to satisfy an efficient, reliable and stable process.

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During the argon-oxygen-decarburization (AOD) process high-chromium steel melts are decarburized by oxygen and inert gas injection through sidewall tuyeres and a toplance. The tap-to-tap time of the AOD process depends mainly on the time which is necessary to produce a homogeneous distribution of all required components in the melt. This mixing time is correlated to the process time. Shorter tapping times lead to a higher productivity, lower energy consumption and lower operating costs. Prior to the reduction stage, the mixing behavior influences the melting of the solid slag layer after the addition of ferro-silicon. Fast and efficient melting of the solid slag compounds is essential to attain sufficient reduction rates. Conventional approaches to experimentally investigate the mixing efficiency in aqueous models (e.g. the 95%-mixing time criterion), yield results which show a large variance concerning the mixing time for a single operating point. In the present study a novel approach for the determination of the mixing time in a water model of an AOD converter is presented and verified. The results show a lower variance and an increased reproducibility as compared to the prior measurement technique. Using these experimental results, the vessel shape and the required volume flow rate of the AOD process gas can be optimized. Furthermore, numerical simulations can be validated using the presented results. The measurement technique can be utilized in water models representing other metallurgical processes.

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Due to an ever‐increasing demand for product quality, a comprehensive understanding of the flow behavior of molten steel inside the continuous casting process is necessary. To investigate flow phenomena in a CSP‐mold, a 1:1 water model corresponding to a continuous casting plant with tundish, stopper rod, SEN, and mold is used. In the present study the flow at the SEN entry section was investigated regarding different stopper rod tips and volume flows as well as the connected influences to the mold flow. To identify the influence of the stopper tip designs to the flow inside the SEN, the industrial used elliptical stopper tip was compared with two different tip geometries which are conical and spherical. For the investigations the Particle Image Velocimetry (PIV) has been applied. The average velocity, the turbulent kinetic energy, and the pressure distribution inside the SEN are highly influenced by the stopper tip geometry. For different configurations of stopper tips as well as different volume flows absolutely different flow patterns are measured. Furthermore the obtained velocity fields inside the mold potentially give the information that the flow arising there is influenced by the shape of the stopper tip.